1. Field of the Invention
The present invention generally relates to restoration strategies in ATM transmission systems, and in particular to a permanent virtual circuit (PVC) management method and system in an ATM switch for restoring data transmission when a fault occurs on a transmission line between ATM switches.
2. Description of the Related Art
Asynchronous Transfer Mode (ATM) communications are becoming widely used to allow various kinds of data of different bit rates to be transferred at high speeds, which is expected to realize the Broadband Integrated Services Digital Network (B-ISDN). In an ATM switched network composed of a plurality of ATM switches, a permanent virtual circuit (PVC) is established to provide a point-to-point connection through a plurality of ATM switches. Since PVC is a static connection, however, when a failure occurs on a transmission line between ATM switches, ATM cell transmission becomes impossible.
To avoid such a breakdown of communications, there has been proposed an ATM switch having a restoration function in Japanese Patent Unexamined Publication No. 9-247153. This conventional ATM switch is provided with a VPI/VCI conversion table storing a set of VPI and VCI for working path and another set of VPI and VCI for protecting path for each cell. When a failure is detected on a working line, the call on the working line is switched to an alternative line without call interruption.
An object of the present invention is to provide a PVC management method and system which can achieve rapid fault recovery when a fault occurs on a transmission line between ATM switches.
Another object of the present invention is to provide a method and system which can achieve automatic fault recovery with simplified procedures.
According to an aspect of the present invention, in a system for managing a permanent virtual circuit (PVC) including a plurality of ATM switches in an ATM network including a network management system, each of the ATM switches includes a pair of an incoming header translator and an outgoing header translator, which are provided for each line; and a PVC controller controlling the incoming header translator and the outgoing header translator to provide a working PVC and a protection PVC which are associated with different transmission lines, wherein the working PVC and the protection PVC are selectable under control of the network management system.
The PVC controller may control the incoming header translator and the outgoing header translator such that the working PVC is set up and the protection PVC stands ready to be set up, wherein, when a failure occurs on a transmission line associated with the working PVC, the protection PVC is set up to ensure cell communication in place of the working PVC. When the transmission line associated with the working PVC has been restored, the working PVC is set up to ensure cell communication in place of the protection PVC.